1. Field of the Invention
The present invention relates to the field of temporary fasteners, as are typically used to hold work pieces together while permanent fasteners are installed.
2. Prior Art
Temporary fasteners are frequently used in manufacturing to hold work pieces together while permanent fasteners are installed. Such fasteners are installed in a few holes in the work pieces to align and pull the parts together that are to be joined so that permanent fasteners may be installed in the remaining holes, after which the temporary fasteners are removed for installation of permanent fasteners in these holes also.
Ideal temporary fasteners may have various characteristics, depending on their application. In general, as previously mentioned, temporary fasteners are intended to align and pull the parts together so that permanent fasteners may be installed. Consequently, a temporary fastener should have the capability of pulling together work pieces that may initially have a substantial separation (commonly referred to as xe2x80x9csheet takeupxe2x80x9d), so that the installer does not have to resort to other means to pull the work pieces together sufficiently to properly install the temporary fastener.
Also, while the work pieces will not be subjected to the same loads they may encounter in use after the permanent fasteners are installed, the temporary fasteners typically will only be installed in a small percentage of the fastener holes in the work pieces, such as every tenth hole or so. This, plus a desired large and strong sheet takeup capability, makes temporary fastener strength an important parameter.
Other important parameters for temporary fasteners include low fastener cost, and ease of installation and removal. Simplicity of fastener design and assembly, together with a simple installation operation contributes to low cost and ease of operation, as does a large and strong sheet takeup capability. Removal of temporary fasteners varies with the fastener design, some fasteners being disassembled for removal and others being drilled out for removal. Drilling out of temporary fasteners is perfectly acceptable and may be a favored method of temporary fastener removal, provided the fastener is a low cost fastener and the drilling operation itself doesn""t foster other complications.
In some applications, temporary fasteners must be installable and removable with access to only one side of the work pieces. Fasteners of this type, such as disclosed in U.S. Pat. No. 5,689,873 entitled xe2x80x9cTacking Fastenerxe2x80x9d and assigned to the assignee of the present invention, are referred to as blind temporary fasteners. The present invention is intended for use in applications where access to both sides of the work pieces is available.
Two piece tack rivets and method of forming holes for permanent fasteners are disclosed. The tack rivets have a stem with a head on one end and a grooved region adjacent the other end, and a locking collar for fitting over the grooved region of the stem for deforming into the grooved region of the stem on applying a setting force between the locking collar and the stem. The stem is placed through a hole in the work pieces, the locking collar is put over the stem portion protruding from the other side of the work pieces, and the setting force is applied. Once the rivet is set, the rivet may be later drilled out with a drill larger in diameter than the head of the stem to form the hole for the permanent fastener. Various embodiments are disclosed.